Paper Cup Guitar

Objective

Students will learn that sound is produced by vibrations and how the tension, length, and thickness of a vibrating string affect the pitch of the note produced.

Materials

Stiff paper cups, fishing line or string, paperclip, pushpin

Background

Sound travels through the air as a pressure wave, and guitars produce sound through the vibration of strings. The string vibrations alone do not move enough air to be heard by an audience, however. In order for the sound to be heard, the vibrations of the strings must be amplified.

Acoustic guitars have a large, hollow wooden body. When the strings vibrate, those vibrations are passed along to the wood. The large amount of vibrating wood vibrates the air inside the guitar, creating sound waves. The sound is projected out through the hole in the guitar's body, allowing the audience to hear it.

Procedure

Use a pushpin to poke a hole in the bottom of the cup, as close to the center as possible. Cut a length of fishing line about 18" long and tie a paperclip to one end. Feed the free end of the fishing line through the opening of the cup and through the hole you poked. Hold the cup in one hand and the end of the string in the other; pull the string taut and pluck it with a finger to make sounds.

Discussion/Extensions

What would happen if you used a different size cup? What about a different material? How might it affect the sound produced? Try with a plastic cup, a very large cup, or even a soup can (you will need a hammer and nail to make the hole in a soup can).

Challenge your students to vary the pitch produced by their paper cup guitars. Pulling the string with different amounts of tension will produce different notes, as will varying the length and thickness of the string.

You can make an electric guitar using piezoelectric elements available at electronics stores, audio wires, and computer speakers.